The effect of hydrofluoric acid surface treatment on the corrosion behavior of Mg-Sc alloy

Purpose This study aims to investigate the corrosion behavior of Mg-1Sc alloy in the 3.5 Wt.% NaCl solution following immersion in HF solution for varying durations, which results in the formation of fluoride layers of different extents on the alloy surface. Design/methodology/approach The microstructure and corrosion behavior of Mg-1Sc alloy with different immersion time in the HF solution were both analyzed. Findings The results show that after acid pickling, the surface morphology of the Mg-1Sc alloy varies with pickling time. HF10 exhibits the most uniform surface, while longer pickling times lead to the appearance of obvious corrosion pits. The corrosion resistance of the alloy is found to be dependent on the pickling time, initially increasing and then decreasing. The charge transfer resistance (Rp) of the HF10 sample reaches 6200 Ω·cm², significantly higher than that of the untreated alloy (2430 Ω ·cm²), indicating optimal protective performance at 10 s immersion. Originality/value The alloy shows the best corrosion resistance after 10 s of pickling, surpassing that of the unpickled alloy. As pickling time increases, the F element content on the alloy surface rises. However, at 30 s of pickling, the corrosion products become uneven, and the alloy surface is prone to corrosion cracks and pits, which hinder further improvement in corrosion resistance.